Integrating Past, Present, and Future Approaches - Spatial Mathematics: Theory and Practice through Mapping - page 229

Tools toolbar, select Find Route. On the Find Route tool, under Options, select
the North American Routing Service (ArcGIS Online). On the same Options
screen, check the box “Name locations added with tool using nearest address”
and choose the following address locator: 10.0 North America Geocode Service
(ArcGIS Online). On the same Options screen, mark the “Add route to map
as” option as your choice of a graphic or a shapefile, with the symbology set
to a red line.
Still on the Find Route tool, under the Stops tab, use the arrow with the dot to
add your 7 stops as identified above. You might need to consult another data
and map source to determine the locations of these seven landmarks in New
York City. At the bottom of the window, select “Return to” (the first stop) so
that you have a round trip. Then, select Find Route. Describe the results. Why
do you suppose the return route followed the highway adjacent to the Hudson
River instead of going back the same way? It did so because the highway is
the fastest way through Manhattan, being adjacent to the river, the number of
traffic lights is markedly fewer, there are a greater number of lanes, and the
posted speed limit is higher. Next, experiment with the options. How does
adding one stop, changing the order of stops, adding a barrier, adding a time
window, or changing the impedance from “time” to “length” affect the final
route? In Figure 10.11 , it was estimated that 10 minutes would be required at
each stop. How did this affect the overall time? No matter where you added
the stops, each stop adds to the total time required. What kinds of mathemat-
ics are behind these accurate geocoding and routing services? The mathemat-
ics are complex, considering the attributes on each street segment, including
average and posted speeds, one-way versus two-way streets, number of lanes,
traffic, and time of day. Some of these attributes need to be included in the
geodatabase before the analysis, and some can be added or adjusted by the
data analyst as the analysis is being conducted. Either way, as we have seen
throughout this topic, data quality matters. Do you see why the “Manhattan”
distance does not have unique geodesics? In a typical grid pattern there are
generally two shortest routes to go from the southwest corner of a block to
the northeast corner of the same block. The distances here are all based on
large scale data, and map projection differences at large scales are minimal.
10.4.4 Routing exercise: Determining best route for trucking goods
across the USA
Now that you have had some practice with a local routing activity, you next
have the opportunity to perform some analysis at a national scale for the
USA ( Figure 10.12 ) . Consider the following scenario: The Geo-Trucking
Corporation, which delivers handheld mobile devices for field collection, needs
to hire someone to drive a truck each week from Boston to Boise, and return,
with intermediate stops in Birmingham, Alabama and Fort Smith, Arkansas.
The Geo-Trucking Corporation has hired you to determine the most efficient
route for this weekly trucking operation. To complete your task, you will use